Means and hethod fob



K. S. JOHNSON MEANS AND METHOD FOR SIGNALING 2 Sheets-Sheet 1 File Sept. 5, 1919 f /g. /.w 5

/r7 ven for Kerr/1 27/1 D. Johnson Oct. 16 I923. 1,470,986

' K. s. JOHNSON MEANS AND METHOD FOR SIGNALING Fil Sept. 1, 1919 2 Sheets-Sheet 2 /n ve/vfors Ken/7.97% 5. Johnson b Affy.

a three-wire line Patented Oct. 1 6, 1923.

UNITED STATES I 1,410,986 PATENT OFFICE.

KENNETH S. JOHNSON, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MEANS AND METHOD FOR SIGNALING.

Application filed September 5. 1919.

To aZZ whom it may com-writ.

Be it known that I. Ki-zxxn'rn 5'. JOHN- suN, a Citizen of the United States. residing at Jersey City. in the county of Hudson, State of New Jersey. have invented certain new and useful Improvements in Means and Methods for Signaling, of which the l'ollovw ing is a full. clear. concise. and exact description.

This invention relates to a telephone sys tem and a method of operating the same which is especially adapted to environnwnts where there may be considerable disturbing noise at either or both of the substations. and the principal object in rice is to secure maximum or relaivcly high transmission efiiciency over a line of substantial length in connection with the complete elimination of interference with the receiver by the transmission encrgy originating at the same station.that is to say elimination of side tone.

The invention includes more particularly circuit whose essential characteristic is that. the transmission of telephonic currents in one direction is eti'cct ed by only two of the three wires which, for convenience. mav be referred to as the outside" wires. while in the other direction it. is efl'ected over these same two wires. acting in parallel for one side of the line and over the third or neutral wire or conducting path. acting ['or the other side.

The invention further includes such a re lation of the substation apparatus to the wires of the line circuit as will insure the distribution of the line constants symmetrically among the three wires. thereby efi'ecting perfect balance between the limbs of the line during transmission in either direction.

Thus. the two outside wires are connected at their ends by impedance elements and the neutral conducting path has a connection with each impedan e element in such relation that the impedance between sa d path and one of the outside wires is equal to the impedance between said path and the other out side wire: and the receiver oi one station and the transmitter of the other station are electrically associated with the neutral wire. while the transmitter of the first station and the. receiver of the second station are clcctrically associated with the two outside wires in such manner as to maintain the bail ance of the lines and to insure that the re- Serial No. 321,889.

ceiver of the transmitting station will not be affected by the energy originating at. that station. The circuit arrangements are preferahly. although in most cases not necessar ily, such as to insure that there will be no transmission loses due to the passage of voice currents through the transmitter 0 the receiving station.

here all three wires arev used for the transmission of energy there is less attenuation loss with consequently more effective transmission in that direction than where the transmission is effected in the other direction over the outside wires. For lines of short length this characteristic is immatcrial. For lines of considerable length a substantial advantage may be realized by arranging the circuit so that the transmission over the three wireswill be from the station whose transmitting efficiency, under normal conditions. is the lower.

While the substation sets are not connected in the same manner at; the two ends of the line they may. in most instances. consist of identically the same apparatus. Each set may consist (1) of a. three-terminal receiver and a two-terminal transmitter-or, (2) a three-terminal transmitter and a twoterminal receiver or. (3) a two-terminal transmitter and a. two-terminal receiver. one or both associated with an induction coil.

Figs. 1 to 12.01 the accompanying drawings are diagrams showing variations. as regards details of the line circuit, the substation circuits and the connection of the substation sets at the two ends of the line, in a system in which the essential features of the invention are incorporated.

Fig. 1 illustrates a line circuit as above described in connection with the preferred arrangement of substation sets and may be regarded as typical. The line circuit comprises the outside wires 1 and 2 connected at their ends by the windings 3 and 4 of induc tion coils. and the neutral wire 5 the ends of which are connected at. the middle points of said windings. At both stations the transmitters and receivers are in local circuits inductively related to the line circuit. At station A the transmitter is in circuit with the supply battery 6 and the winding 7 of an induction coil which is completed by the winding .5 in the line circuit: and the receiver is in another circuit with the winding 8 of an induction coil which is completed by -At station with the winding 13 of an induction coilwhich is completed by the winding 4 in the line circuit.

When A is the transmitti station, the current induced in the coil 3 ows over the wire 1 throu h the coil 4 and back throu h the wire 2. ince the ini dance bctween't e wire and either of t e wires 1 or 2 is equal to the impedance between the wire 5 and the other outside wire, there is no difierence in potential at any given instant between the ends of the wire 5, and it follows that no current flows through said wire and hence no energy is transmitted to the receiver at station I nor to the transmitter at station B.

When B is the transmitting station the current induced in the coil 12 flows through the wire 5 and induces a current in the 01!- cuit which includes'the receiver at station A. ,The current transmitted by the wire 5 divides at the windings 3 and 4 and flows in ogposite parallel relation through them and t rough the wires 1 and 2 which thus form one sde of the line circuit, the wire 5 forming the other side. The division of the current at the middle points of the windings 3 and 4 preventsany inductive effect nd consequently no energy is transmitted to the receiver at the station B nor to the transmitter at station A, while the windings 3 and 4 present no impedance but merely the r ohmic resistance to the voice currents,

According to Fig. 2 the local circuit of the receiver at station A is eliminated and the receix'cr is interposed serially in the wire 5. In other respects the arrangement shown in Fig. 2 s similar to Fig. 1. The same variation is carried out in the arrangements shown in Figs. 3 to 6, 8, 9. 10 and 2.

The arrangement shown in Fig. 3 introduces a further variation according to which the receiver at station 13 is bridged across the wires 1 and 2. and is in shunt to an impedance coil 4. also bridged across the wires and which lakes the place of the winding 4 as the impedance element. In this case it is obvious that when A is the transmitting station there will be no difference in potential. at any given instant between the ends of the wire 5 and the voice currents will not.therefore. pass through receiver at station A. The receiver at station B will be actuated however. W'hen B is the transmitting station. there will be no difference in potent al at any given instant between the ends of the shunt in which the receiver at that station ishrranged; hence the energy will be transmitted to the receiver at station A, but will not be transmitted to the receiver at station B.

in Fi 4 the transmitter andv battery 6 at station E are bridged across the wires 1 and 2 and are in shunt with an impedance coil 3" also brid ed across said wires, and which takes the pl ace of the winding 3 shown in Figs. 1-3. This figure also shows a further variation in the connection of the set at station-B, according to which the transmitter and battery 10 of that station are in series in the wire 5 in a substation arrangement otherwise similar to that of Fig. 3. As in the preceding instances, when A is the transmitting station there is no difference of potential at. any given instant between the ends of the wire 5. When B is the transmitting station there is no difference of potential at any given instant between the ends of the shunt in which the receiver of station B is arranged, similarly to the arrangement shown in Fig. 3; in a like manner there is no difference of potential at any given instant between the ends of the shuntin which the transmitter of station A is arranged. Hence the energy originating at station B will be transmitted to the receiver at station A, but will not be transmitted to the receiver at station B nor to the transmitter of station A.

F i 5 shows the transmitter and battery 10 0' station B in series with the wire 5 in an arrangement otherwise similar to that of ig. 6 shows an arrangement similar to that of Fig. 2, exec t that the receiver at station B is of the t rec-terminal type and is arranged serially in the wires 1 and 2; and the wire 5 has its end'at station B connected to the middle point of the receiver windings which thus constitute the impedance element. In this case the receiver will provide a low impedance path for the alter hating currents originatingat the same station, providing its windings be perfectly coupled and of the same impedance.

In the circuits of Fi .3, 1-6, each substation has its local battery lhr supplying currentto the line. Figs. 7, 8 and 9, however. show circuits in which the current supplied to the transmitters is provided by a common bah tcry 14. serially arranged in the wife 5.

In Fig. 7 the wires 1 and 2 at station A are connected by an induction coil 3. and the transmitter at that station is connected in shunt with this coil by taps so arranged as to secure the requisite transformer action in transmitting from station A to station B. As shown, the shunt in which the transmitter at station A is arranged has its taps taken from the middle point of the winding 3 and from the middle point of one of the halves of this winding. In any case a condenser 15 is in series with the coil 3" between the taps of the transmitted shunt in order to divert the steady current from the battery 14 with full effect through the transmitter at station A. The wires 1 and 2 at stati n li are connected by an impedan e winding in any of the ways dew-ribed. the arrangement of Fig. l where the re ent-l of station it is inductively reltltt'tl to the circuit of the line being shown. The wire 5 is connected to the middle points of the windings at both stations in order that there may be no ditl'erence in potential between its ends at any given instant, when transmitting from station A to station B. At station the wire 5 divides the windings of coil 3 into to o babes which. in transmitting from station B to station A. are without transformer and. therefore. oppose no impedance to the flow of the telephonic ell! rents over the wire 3. The transmittc at Station B is conne ted in shunt with an induction coil 12 arranged serially in the wire the taps of the shunt. of course, being. ta ken so as to secure the requisitctransformer action in transmitting from station B to station A. A condenser 16 is in series in the bridge across the laps of the shunt in order to divert the battery current through the transmitter at station B.

Figs. 4 and i) show the circuit in connection with a two-button transmitter in series with the wires 1 and :2 at station A. and which constitutes the in'lpedance element, the wire 5 heing connected to the middle or diaphragm te minal of this transmitter and the transmitter at station B being in series in said wire. in Fig. t the receirer of station ii is connected to the wires 1, 2 and 5 in the same manner as in Fig. 6. whereas in Fig. it it is inductively related to the line circuit similarlv to the arrangement shown in Fig. l. .\s in the revious instances. the impedanr betwe n the wire 5 and one of the onlshle ires is rental to the impedance betw n the n ire Ii and the other outside wire. The ("l('|lil.- of Figs. h aul i are theoretically not so ellicienl as the circuits of the preceding lignres since when station B is transmitting some ol' the energy will be dissipated in the two button transmitter of station A. However. this disadvantage will not he noticeable in nit-st o'l' the'condh tions of practice. particularly where the lines are short. The specilie circuit ar rangements of Figs. R and t) have been made the ubject matter of another application tiled in my name. Serial No. 321.890, tiled September 5. i919.

Figs. Hi. I] and 1:2 are-schematic examples of circuits having the charzu'teristic features above set forth and in which mechanical repeaters are employed where it may be desirable to augment or amplify the voice current in Fig It) repeaters are provided only at the transmitting ends. The transmitter and battery 6 of station A are in a local circuit with the repeater reoever element 17: and the primary winding of the induction unit by which an l'l. M. F. is impressed on the line is in another local ircuit with the repeater transmitting element 18 and a battery (1. the seeondarv winding of the coil being conne ted to the wires 1. 2 and 5 in the manner shown in Fig. l. The wires 1. L and .i and the receiver at station B may be connected up in any of the ways previously described. the arrangement of ig. I being shown. At this station the trans mittcr is in a local circuit with the battery It) and repeater receiving element 19: and the repeater transmitting element 20 is in series in the wire 5 together with the line battery 14. \Vhen transmitting from station A, the repeater as actuated by the tele )honc transmitter impresses an amplified l). M. F. upon the primary winding of the transformer and the current induced in the line flows in the manner above described, the energy being dissipated in he distant receiver of station B but not being t1 nsmitted to the receiver of station A. When transmitting from station B an amplified E. M. F. is impressed directly upon the line, and since the secondary windings of the induction coils ofi'er parallel opposing paths t the resulting current, the receiver of Station A alone will be energized and no energy will be transmitted to the receiver of station B nor to the transmitter of station A.

in Fig. ll repeaters are provided at the receiving ends only. At station A the telephone receiver is in a local circuit with the battery 21 and the repeater transmitting element: and the repeater receiving element is in series in the wire 5; while at station B the telephone transmitter is in series in the wire 5 with the line battery 14. the repeater receiving element is in a local circuit with the Hcondary windin of the induction coil and the telephone receiver is in another local circuit with the battery 10 and the repeater transmitting element.

In Fig. 12 the repeaters are shown at intcrmediate points of the line which in this instance consists of two three-wire sections distinguished as (i and l). and each having the essential circuit characteristics above do scribed. The section has wires 1*. 2" and 5 and the section D ires 1". 2" and ti J'OIYK sponding to the wires l. 2 and 5 of the circuits shown in the preceding figures. the wires 1 and 2 and the wires l and 2* being connected at the adjacent ends of the sections by the respective windings of a repeating coil 22. and the wires 5" and 5* being connected at the middle point of the corresponding windings of said coil. At the opposite ends of the line the wires 1* and 2 and 1" and 2 are connected by impedance windings in the manner previously described, the wires 5 and 5", of course, being connected to the middle points of the corresponding windings. The sections C and D are provided with batteries 23 and 24 arranged serially in the pective wires 5" and 5. The symmetry of t e circuit is main tained for transmission from station A, for example, by emplo ing a pair of repeaters 25 whose correspon leg elements are bridged in series across the wires 1" end 2 a battery 26 belt! 7 arranged symmetrical v in the bridge w ich connects thetrsnsmitting elements of the repeaters; and for transmission from station B, by arranging the receiving and transmitting elements of. a single rcpeater serially in the respective wires 5" and 5". Coils 28 are arranged serially in the wires 1 and 2 between the connections with said wires of the receiving and transmitting elements of the respective repeaters 25; these coils are of low resistance and ure'so wound on a common core as to offer extremely high impedance to currents which, in transmission from station A to station B, wou d tend to flow in the outside wires past the connections of said wires with the repeater receiving elements but to offer no impedance to currents which, in transmission from station B to station A How over the wires 1" and 2 as used in parallel for ,one side of the line.

When transmitting from station A there is no difference of potential at any given in stant between the ends of the res ctive wires 5 and 5"; hence the wires 1 an 2" are used in series to provide for the operation of the repeaters 25. The induced current originating at station A is confined by the coils 28 to the receiver elements of the repeaters 25 and flows through these elements in their series relation; current being sngplied to the transmitting elements by the attery 26, the reaters are thu efiective to impress an amplified E. M. upon the primary wind ing of the coil 22 and the energy is thus transmitted to the receiver at station. B in the obvious manner.

\Vhen transmittingfrom station B the wires 1 and 2 act in parallel for one side of section D and the wire 5" acts tor the other side; in section C the action is simiiar. In both sections the current flows through the windings of the several induction coils in a parallel opposing relation and hence no energy is induced in the receiver at station B nor in the transmitter at station A nor in the repeaters 25 of section C due to the presence of current in section T The flow of current through the wires 1''. 2* and 5" in the manner described energizes the receiver element of the repeater 26 and current being supplied by the battery 23 to the transmitter element of this repeater an amplified E. M. F. is impressed upon the line. As above explained, the coils oppose no impedance to voice currents flowing through the wires 19 and 2 as thus nscd in pai-silei in of the line.

It will, of course, be apparent. that the estures of the invention man; in! iin'sorpoi'eteii in circuits cmlmdying versions Rnniiiicat ms in detail from the circuits'ehove dew these are; therefore, to be considered merely as examples of circuits in accordance with the invention and having in su h iiistiiiirc the essential or characteristic cs1 cm; pointed out.

What is claimed is:

1. In a two'way signaling syslsnn 3 inc: circuit comprising two outside linuiclics and it central branch, is transinitl ing iltYlii and a receiving device associated with said line circuit at each end thereof, on ilnpmlunuc element in each of said branches, said isnpedanoe elements having such values; 11m Signaling current flow through oniy two of said branches when signals arc Ewing trans mittedin one direction eml lions all three branches when signals are being transmitted in the opposite direction and a receiving; deiice coupied to that branch through which no current-firms for transmission in one direction.

2. In a. two-way signaling svstcmi a iinc circuit comprising two outside iiriinches and a central branch, s transmitting device and a receiving device associated with said lino circuit at each end thereof, an impedance element in each of said outside branch 2, said impedance elements having such Vhiihcs that signaling current flows thniegh only two of said hrenches when signsis are being; transmitted in one direction and through all the lliiifi when tinmr mitting in opposite direction, one of receiving devices being couple-:1 the? ii branch through which no cnrrcnt flows for transmission in one direction. said other receiving device being coupled serisily to those branches that. contain the signaling current when thc transnii sion occurs through only two of said branches.

in a lWfiWBY signal 7 circuit comprising" two ontsnse hranchos tiiifl a centre condncii path enimlnctanco at each end of said cir cit; snid outside branches being serially connects ei their ends by said indnctances, e transmitter inductively coupled. to one of said inductonces, it re ceiver ii'nlnctirciy songs-ti is;- lhc other o: said ililllltitifltffiig and e St'inriici transmitter and second receiver in ssid centre-l ducting iath one of said receivers recei substantially none of the t-ransrn energy from one of said transmitters 4, in s twoorsy signnims; system,

transformers, said central branch being connected to an intermediate point of said windings, connections whereby signals from one of said substations is impressed on said outside branches in series relation, and connections whereby signals from theother of said substations is impressed on said outside branches in parallel relation, the impedance of said outside branches and said windings being such that said substations are anti-side tone 5. In an electric system, a plurality of substation sets, a three-conductor circuit terminating at one end in one' of said sets and at the other end in a second of said sets, means for coupling the transmitter of one of said sets to one of said conductors, means for coupling tie receiver of a second set to the same condlctor, means for coupling the receiver oi" the first set to the other two conductors, and means for coupling the transmitter of the second set to said two other conductors, said means being so adjusted as to render said sets anti-side tone,

6. A two-way signaling system compris ing a plurality of signaling sets, a three conductor circuit terminating at one end in one of said sets and terminating at its other end in a second of said sets, each set cone prising a transmitter and a receiver, an impedance at each end of said circuit, said impedances being connected serially with two of said conductors, the transmitter of said first set being coupled with one of said impedances, the receiver of the second set being coupled to the other of said impedances, the receiver of said first set and the transmitter of the second set being oupled to the third conductor of said circuit, said third conductor being so connected to intermediate points of said impedances that said sets are anti-side tone.

7. A two-way signaling system comprising a plurality of signaling sets, each conr rising a transmitter and a receiver, a three- "omllictOr circuit. terminating at one end in one of said sets and terminating at its other nd in a second of said sets, means for coupling one transmitter to said circuit whereby currents therefrom are impressed se rially on two of said conductors, means for coupling the transmitter of the second set to said circuit whereby currents therefrom are impressed on the two conductors in parallel, and means for coupling the receiver of the first set and the receiver of the second set to said circuit whereby said sets are anti side tone.

8. In a signaling system, an impedance element, a signaling line having one end connected to a terminal of said element, a second signaling line having one end connected to the other terminal of said element, a second impedance element joining the op positc ends of said lines, a third line connecting intermediate points of said imped ances, a signaling set at one end of said lines and comprising a transmitter and a receiver, means for impressing signals from said transmitter upon said lines in such a manner that the points where said third line is connected to said impedance elements are at the same potential for said currents, said receiver being coupled to said third line whereby said receiver receives none of the signals from said transmitter, a second signaling set at the other end of said lines and comprising a transmitter and a receiver, the transmitter of the second set being coupled to said third line, and the receiver of said second set being so coupled to said second impedance that said second receiver receives none of the signals from the second transmitter.

9. In a signaling system, two substations, a line circuit therehetween comprising two outside branches and a central conducting path, a repeater cimnected across said branches and having input and output terminals, and an inductance having a wind ing connected between said input terminals and said output terminals, said inductance having a high impedance for currents flowing serially in said branches but having a low impedance for currents flowing in parallel in said branches.

in witness whereof, I hereunto subscribe my name this 2nd day of September A. l).,

KENNETH S. JOHNSON. 

